Molecular dynamics study on the growth mechanism of goethite (alpha-FeOOH) nanorods

This study employs molecular dynamics (MD) method to fundamentally understand the growth mechanism of one-dimensional goethite (alpha-FeOOH) nanostructure, which can be generated by a simple hydrochemical method assisted by the surfactant of cetyltrimethylammonium bromide (CTAB) under mild conditions. In this approach, various surfactants were investigated for testing their effectiveness during the formation and growth into nanorods, further confirmed by the calculation of the interaction energies between goethite surfaces with surfactant molecules. It was found that the efficient surfactant/additive prefers to interact with the (xy0), i.e., (100), (010) and (110), but weakly on the (xy1), i.e., (101), (011) and (001) surfaces. The results can be used to explain the formation and growth mechanism of goethite nanorods. The interactions were found to be highly dependent on the electrostatic energy of the functional groups in the molecule which allow the strong interaction on a certain goethite surface. The findings can provide quantitative information for understanding nanoparticle growth, and useful for optimizing surface acting agents (surfactants or polymers) for shape control of nanoparticles with desirable functional properties. (C) 2010 Elsevier Masson SAS. All rights reserved.